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LTC6602 input connection

Category: Hardware
Product Number: LTC6602

Hi,

I would like to use LTC6602 as filter for IQ demodulator. My modulator is MAX2021, which has differential output impedance of 53ohms. My signal has maximum frequency 640kHz and I'm would use ADC sampling rate of 2MHz - 4MHz. I would need DC block for LTC6602.

I'm planning to use circuit from this thread:  LTC6602 input and output

Instead of DC coupled single ended input, I need to modify input for AC and differential. I would use LTC6604-2.5 for output.

My question is what is optimal input circuit of LTC6602 as my source is low impedance? According to datasheet Figure 12b, it is recommended to have 1.87k resistors for bias. If I connect MAX2021 directly before 0.1uF in Figure 12b, I would get double to voltage. Would that be recommended way to use LTC6602 for low impedance AC coupled loads?

  • Hello,

    Sorry to miss this thread. Some distortions on the output is expected especially if you have >50pF loads. But the 50ohm or 100ohm series resistor should help with that. Can you try connecting a snubber network (series RC to GND) on the output just to check if it will help with the oscillation? Typical values should be 140ohm and 10nF for caploads of <300pF.

    Best Regards,
    Kenneth